Overhauling the transmission means renewing as many of the wear and damage-prone components in the selector drum assembly as possible.
This will attain the best results, as interfacing used parts with new will lead to premature wear of the new parts, and notchy gear selection.
Other selector drum and fork related parts you may wish to purchase:
Pro workshop gasket sealant: 08C70K0234M for a more professional result. Add as many items as you wish to the same shopping cart, new shift-shaft 2541127A00 and gear-sift Cam-drive 2532231302 for example, and still only pay the same single fixed price shipping cost. This component may have other applications in the Suzuki model range so please ensure the part-number/s you order are correct for your particular model.